The applicant's current research involves speech understanding and sound localization for unilateral and bilateral cochlear-implant (CI) users. Specifically, the applicant studies the inclusion and detection of pinna cues for median-sagittal-plane sound localization in CI users. It involves speech understanding experiments, experiments with direct multi-electrode stimulation, and sound localization experiments. The applicant also continues to work on dynamic binaural phenomena, which was his dissertation topic at Michigan State University. Dynamic binaural phenomena are related to understanding speech in difficult listening conditions, like reverberant or noisy rooms. The proposed research will be a natural continuation of the post-doc and dissertation research areas. It aims to combine the areas of speech understanding, binaural hearing, sound localization, and cochlear implants. The proposed research is novel because it aims to understand the advantages, capabilities, and limitations of bilateral CIs under controlled multi-electrode stimulation. Controlled multi-electrode stimulation research has only started recently;much of this research is being performed at the sponsor's lab. Research on this topic is a logical next step in bilateral CI research;it would help provide understanding of an important advantage of bilateral implantation, that of understanding speech in noisy environments. The main hypothesis driving this work is that current CI systems introduce fundamental differences from the healthy auditory system, and these differences alter important acoustic information enough to significantly diminish any binaural hearing advantage. Some of these limitations may be compensated by different processing schemes, while others are intrinsic to electrical stimulation and cannot be compensated with the current generation of CIs. The mentored phase of the proposed research will focus on single- electrode binaural signal detection. The independent phase of the proposed research will focus on multi- electrode binaural signal detection and speech understanding in realistic listening environments. The ultimate aim is to provide a binaural advantage to bilateral CI users'speech understanding. RELEVANCE: The main goal in the field of cochlear implants is to provide better speech understanding for profoundly deaf individuals. A major research question in this field is hearing with two ears. The proposed work will systematically examine factors that may cause a difference in acoustic perception between cochlear-implant and normal-hearing listeners. These studies will guide the design of future cochlear implants.